1. Field of the Invention
The present invention relates to a coupling apparatus including a release preventing device.
2. Description of the Related Art
A coupling apparatus which includes a pair of couplers having the same structure as to each other and to be coupled with each other only by moving them closer to each other after they are coaxially arranged is known from Japanese Patent No. 3107507.
A structure of the coupling apparatus concerning this patent will now be described with reference to FIGS. 41 to 43. FIG. 41 shows a perspective view of a pair of couplers 10a and 10b in a state that they are separated from each other. FIG. 42 shows a side view of one coupler 10a shown in FIG. 41 and a vertical cross-sectional view of the other coupler 10b shown in FIG. 41.
Each of the pair of couplers 10a and 10b comprises a cylindrical coupling main body 12. A plurality of projecting portions 14 are formed at a plurality of positions separated from each other at equal intervals in a circumferential direction on one end surface of the coupling main body 12. Each of the projecting portions 14 projects outward in a direction equal to an extending direction of a longitudinal center line of the coupling main body 12.
In each of the projecting portions 14, one side surface 14a facing in one circumferential direction of the coupling main body 12 extends in the direction equal to the extending direction of the longitudinal center line. On the one side surface 14a, an engagement piece 16 protruding in the one circumferential direction mentioned above is formed at a position adjacent to a projecting end of the projecting portion 14.
FIG. 43 shows the projecting portions 14 and 14 of the coupling main bodies 12 and 12 in a state that the couplers 10a and 10b are coupled with each other, in an enlarged manner. As well shown in FIG. 43, the engagement piece 16 includes an engagement surface 16a extending in a circumferential direction of the coupling main body 12 and facing in a direction opposite to the projecting direction of the projecting portion 14. The engagement surface 16a is inclined in such a manner that a base end of the engagement surface 16a at a base of the engagement piece 16 is positioned outward from a protruding end of the engagement surface 16a at a protruding end of the engagement piece 16 in the projecting direction of the projecting portion 14. A stress relaxation groove 17 having a substantially U-shape is formed on the one side surface 14a of the projecting portion 14 at the base end of the engagement surface 16a. The stress relaxation groove 17 prevents a stress loaded on the engagement surface 16a from concentrating on the base end of the engagement surface 16a. 
The other side surface 14b facing in the other circumferential direction of the coupling main body 12 in each of the projecting portions 14 is inclined in such a manner that a base end of the other side surface 14b is closer to the adjacent projecting portion 14 as compared with a projecting end of the other side surface 14b. An urging unit 18 is set at a predetermined position on the inclined other side surface 14b. The urging unit 18 includes a cylindrical cup shaped case 18a embedded in the inclined other side surface 14b at the predetermined position. A compression coil spring 18b and a ball 18c are accommodated in an inner space of the cylindrical cup shaped case 18a. The compression coil spring 18b urges the ball 18c toward an opening of the case 18a. Since a diameter of the opening is set slightly smaller than a diameter of the ball 18c, the urged ball 18c does not jump out from the opening.
Tool engagement grooves 20 are formed on an outer peripheral surface of the coupling main body 12.
A cylindrical liner 22 is fixed on a region near to the projecting portions 14 in an inner peripheral surface of the coupling main body 12. One end portion of the liner 22 positioned near to the projecting portions 14 is surrounded by the projecting portions 14 of the coupling main body 12, and protrudes between the projecting end and the base end of each of the projecting portions 14 of the coupling main body 12. An annular seal member 24 is attached on a protruding end of the one end portion of the liner 22. A region positioned away from the projecting portions 14 in the inner peripheral surface of the coupling main body 12 is configured as a rod-like or tubular member fixing portion 26 to which an end portion of a rod-like member or a tubular member is fixed. In the conventional coupling apparatus shown in FIGS. 41 to 43, one end portion of a fire hose 28 is fixed to the tubular member fixing portion 26.
In order to couple the pair of couplers 10a and 10b of the conventional coupling apparatus having the above-described structure with each other, at first, the couplers 10a and 10b are coaxially arranged in such a manner that the projecting portions 14 of one coupler 10a are opposed to a plurality of indents between the projecting portions 14 of the other coupler 10b. Then, the couplers 10a and 10b are moved closer to each other, and the projecting portions 14 of the one coupler 10a are inserted into the indents between the projecting portions 14 of the other coupler 10b. Immediately before the protruding ends of the projecting portions 14 of the one coupler 10a reach bottom surfaces of the indents between the projecting portions 14 of the other coupler 10b, the ball 18c of the urging unit 18 in the inclined other side surface 14b of each of the projecting portions 14 of the one coupler 10a comes into contact with the ball 18c of the urging unit 18 in the inclined other side surface 14b of each of the projecting portions 14 of the other coupler 10b. Then, the urging units 18 urges the pair of couplers 10a and 10b in such a manner that they are separated from each other along the longitudinal center line of each of the coupling main bodies 12 and they are rotated in the circumferential direction of each of the coupling main bodies 12. As a result, circumferentially protruding ends of the engagement pieces 16 of the projecting portions 14 of the one coupler 10a comes into contact with circumferentially protruding ends of the engagement pieces 16 of the projecting portions 14 of the other coupler 10b. In this state, when the pair of couplers 10a and 10b are further moved closer to each other against urging forces of the urging units 18, the circumferentially protruding ends of the engagement pieces 16 of the projecting portions 14 of the one coupler 10a and the circumferentially protruding ends of the engagement pieces 16 of the projecting portions 14 of the other coupler 10b slide on each other in a direction along the longitudinal centerline. At last, as shown in FIG. 43, the inclined engagement surfaces 16a of the engagement pieces 16 of the projecting portions 14 of the one coupler 10a are engaged with the inclined engagement surfaces 16a of the engagement pieces 16 of the projecting portions 14 of the other coupler 10b in the direction along the longitudinal centerline. This engagement is maintained by the above described urging force.
At this time, the seal member 24 of the liner 22 of the one coupler 10a comes into contact with the seal member 24 of the liner 22 of the other coupler 10b, thereby sealing a gap therebetween.
When pressurized water is flowed in the fire hose 28 while the pair of couplers 10a and 10b are coupled with each other as described above, the pressurized water pushes the seal members 24 of the liners 22 of the pair of couplers 10a and 10b outward in a radial direction of each of the liners 22. As a result, the liners 22 of the couplers 10a and 10b are pushed in directions in which the liners 22 are separated from each other along longitudinal center lines of the liners 22. The pushing forces along the longitudinal center lines strengthen the engagements between the inclined engagement surfaces 16a of the engagement pieces 16 of the projecting portions 14 of the one coupler 10a and the inclined engagement surfaces 16a of the engagement pieces 16 of the projecting portions 14 of the other coupler 10b. 
In order to separate the coupled couplers 10a and 10b from each other, the other coupler 10b is moved closer to the one coupler 10a in the direction along the longitudinal center lines against the urging forces of the urging units 18 and then the couplers 10a and 10b are rotated relative to each other while the supply of the pressurized water into the fire hose 28 is stopped and the pushing of the seal members 24 by the pressurized water is stopped. As a result, the engagements between the inclined engagement surfaces 16a of the engagement pieces 16 of the projecting portions 14 of the one coupler 10a and the inclined engagement surfaces 16a of the engagement pieces 16 of the projecting portions 14 of the other coupler 10b are released. Subsequently, the urging forces of the urging units 18 urge the pair of couplers 10a and 10b in such a manner that couplers 10a and 10b are separated from each other along the longitudinal center lines thereof.
The above-described movements along the longitudinal center lines of the pair of couplers 10a and 10b and the above-described rotations thereof, which are required for separating the couplers 10a and 10b from each other, rarely cannot be performed by a human power due to foreign matters such as particles of sand which enter into gaps between the couplers 10a and 10b while they are coupled with each other. In such a case, an appropriate tool is engaged with the engagement grooves 20 on the outer peripheral surface of each of the couplers 10a and 10b, and the above-described movements of the couplers 10a and 10b along the longitudinal center lines and the above-described rotations of the couplers 10a and 10b, which are required to separate the couplers 10a and 10b from each other, can be forcibly performed by using the appropriate tool.
Each of the pair of conventional couplers 10a and 10b as described above has a simple structure, and the conventional couplers 10a and 10b facilitate an operation for coupling them with each other and an operation for releasing the coupling of them. If the rod-like member or the tubular member fixed to the coupling main body 12 is constituted of a material like that of the fire hose 28 which absorbs a certain degree of rotational force loaded thereto, the coupling of the couplers 10a and 10b is maintained by the urging forces of the urging units 18 even when the rotational force is loaded to the rod-like member or the tubular member while the couplers 10a and 10b are coupled with each other and the pressurized water is not supplied to the tubular member.
However, if the rod-like member or the tubular member is not constituted of a material like the fire hose 28 which absorbs a certain degree of rotational force loaded thereto, the coupling of the couplers 10a and 10b may be released when a rotational force larger than the urging forces of the urging units 18 is loaded on the rod-like member, or when the rotational force larger than the urging forces of the urging units 18 is loaded on the tubular member while the pressurized fluid is not supplied to the tubular member.
This invention is derived from these circumstances, and an object of this invention is to provide a coupling apparatus including a release preventing structure, in which: a pair of couplers are coaxially arranging and then are moved closer to each other so that the couplers are rotated relative to each other in their circumferential directions and are coupled with each other in a direction along longitudinal center lines thereof along which the couplers are separated from each other, by urging forces of urging units, when the pair of couplers are coupled with each other, as in the conventional coupling apparatus according to the above described patent; and the couplers coupled with each other are moved closer to each other and are rotated relative to each other oppositely in their circumferential directions against the urging forces of urging units, when the coupling of the couplers with each other are released, also as in the conventional coupling apparatus according to the above described patent: and further in which the coupling of the couplers with each other is surely prevented from releasing even when a rotational force which is greater than the urging forces of the urging units is loaded to at least one of the couplers while the couplers are coupled with each other.